Telephone system



March 25, 1941. P. v. WELCH TELEPHONE SYSTEM 2 Sheets-Sheet l Filed Dec.

WEA/rox? R l/. WELCH 2% @iw/#5W ATTORNEY March 25, 1941. P V, WELCH2,235,910

TELEPHONE SYSTEM Filed Dec. 5, 1939 2 Sheets-Sheet 2 /NVENTOR 4 By R l/.WELCH WWW/M rmfom/Ey Patented Mar. 25, 1941 UNITED STATES PATENT OFFICETelephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application December 5, 1939,Serial No. 307,597

8 Claims.

This invention relates to telephone systems.

The objects of the invention are to improve the equipment employed intelephone exchanges for obtaining and transmitting to subscribers whoare frequently absent from their telephones information with respect tocalls made during their absence; to enable the service operator in theexchange who obtains these messages during the absence of a calledsubscriber to initiate the operation of recording mechanism at theabsentsubscribers substation and to transmit the mes sages over his line tothe substation where they are recorded for his information when hereturns; and to accomplish these purposes without the use of local powersupply equipment or other expensive devices on the subscribers premises.

The foregoing objects of the invention are realized by means of a systemin which a party who has subscribed forthis service is provided with asimple and relatively inexpensive telegraph printer at his substationwhich is wholly under the control of the service operator in theexchange. A calling party who has made an unsuccessful call to one ofthese special service lines and wishes to leave a message for the absentsubscriber proceeds to operate his dial in `accordance with a specialcode to obtain a connection with the service operator in the telephoneexchange. Having obtained the operator, the calling party explains thathis call to the special service line was unsuccessful and gives her themessage he wishes transmitted to the absent subscribers station.Thereafter the oper- -ator obtains connection with the special serviceline over automatic switches and transmits the message by telegraphsignals.

A feature of the invention is a system of this character in which theoperator first transmits a signal over the subscribers line todisconnect the normally effective telephone instrument at the substationand to connect the printer to the line; in which the power for operatingthe printer motor is then supplied from a source at the central officeover the subscribers line to the substation; and in which the operatingcurrent iiowing over the subscribers line to drive the printer motoralso serves to maintain the equipment at the substation in condition forreceiving the telegraph signals which the operator now proceeds totransmit over the line to the printer. An advantage of this system isthat the subscribers substation is normally in condition for the use ofhis telephone, no special operation being required on his part toconvert the substation equipment tothe use of the printer instead of thetelephone. An-

other distinct advantage is that the power for operating the printer issupplied from the central office, simplifying accordingly the equipmentneeded at the substation. p

In the drawings accompanying the detailed specication:

Figs. 1 and 2 illustrate a dial telephone system partly in diagrammaticform and partly in detail embodying the features of the invention.

Fig. 1 illustrates the subscribers lines, one of which is provided witha printer for recording messages, and the automatic switches used inestablishing connections;

Fig. 2 discloses the circuits associ-ated with the service operatorsposition and a telegraph transmitter for sending messages to thesubscribers stations;

Fig. 3 shows a modified form of one of the substations equipped with aprinter for recording the messages; and

Fig. 4 shows ya modified form of the switch calling lines', such as theline I, establish con` nections with other subscribers lines; theconnector switch C--I, by which calling subscribers obtain connectionswith the service operator in the telephone exchange; and the connectorswitch C-2, by which the service operator obtains connections withsubscribers lines entitled to the special service, may be of anysuitable type, such as the switches commonly used in stepby stepsystems.

The subscribers line 2, which is entitled to the special service, isequipped at the substation with a small telegraph printer including adriving motor 3 and a printing magnet 4. The motor 3 is driven byalternating current supplied over the line 2 from the central ofiice,and the printing magnet is operated by direct current telegraph signalstransmitted over the line from the operators position. The substation isalso provided with a gas-filled discharge tube 5 which responds to a.seizure signal transmitted over the line from the operators position toprepare the substation for `an incoming telegraph message. Thesubstation is further provided with a rectier 6 which converts thealternating current flowing in the line to direct current for operatinga relay 1, which disconnects the subscribers telephone set and maintainsthe printer in operative relation to the line for the receipt of theincoming message.

The service operators position in the central office is equipped with atelephone transmitter 8 and receiver 9 for communication withsubscribers who call her for the purpose of leaving messages for theabsent subscribers. Also she has an impulse transmitter I5 for operatingthe automatic switches to extend connections from her position to thelines over which she wishes to transmit these messages. Furthermore, theoperators position is equipped with a telegraph transmitter II forsending the messages over the connections which she has established tothe subscribers lines and with a printer 99 for recording lthe massagessent.

The operators telegraph transmitter and the printers at the substationsmay be of any desired types, such, for example, as those disclosed inthe patent to Zenner No. 2,173,147, of September 19, 1939, and in ZennerPatent No. 2,147,075 of February 14, i939.

The operation of the system will no'w be described, and to this end itwill be assumed that the subscriber of line 2 is absent from hispremises. During his absence the subscriber of ano-ther line, such asline I, may call him. The connection to the called line 2' isestablished in the usual manner over the line-finder switch F, selectorswitch S and connector switch C. Finding the called subscriber absentfrom his telephone and knowing that his line is entitled to specialservice, the calling subscriber releases the unsuccessful connection anddials a special code to operate the selector S and connector C-I toextend his line over the trunk circuit I2 to the service operatorsposition. The connector C--I applies ringing current to the trunk I2,and this current iiows from one side of the trunk I2 through thecondenser i3, thermistor It, lower winding of the relay I5, normalcontacts of key I6 to the other side of the trunk I2. The thermistor I!!becomes heated andlowers its resistance, and sufficient current owsthrough the winding of relay I5 to attract the armature. Thereupon acircuit is closed from battery through the contacts of key II, upperwinding and front contact of relay I5, signal lamp I8 to ground at thenormal contacts of key I6.

The lighted lamp I8 attracts the attention of the operator, and sheanswers the call by moving the key I' to its intermediate position. Theoperation of key It to the intermediate position releases relay i5 andextinguishes the calling lamp I8 and also extends the trunk I2 to theoperators position. The extended circuit may be traced from conductor I9throughthe left closed contacts of key i6, conductor 29, right closedcontacts of said key, conductor ZI, left contacts of key 22, rightcontacts. of key 22, conductor 23, condenser 5lA through the inductioncoil 2G, conductor 25, through the normal contacts and the impulsecontacts 25 of the dial I0, conductor 2l, right 'norma-l contacts of keyI6, left closed contacts of said key to conductor 2B. The operatorconverses with the calling subscriber, who informs her of theunsuccessful call and leaves with her any message that he may care tohave transmitted to the calle-d party.

The operator, having made memoranda of the messages intended for theabsent subscriber, proceeds to establish a connection between herposition and his line. To do this she irst throws the key 22 to theintermediate position to establish a circuit from her impulsetransmitter I9 over trunk 58 to the pulsing mechanism of the selectorswitch S-I and connector switch C- 2. The impulse circuit may be tracedfrom the tip conductor 29, through the left closed contacts of key 22,coil 39, right closed contacts of said key, conductor 3I through theimpulse contacts 2G of the transmitter Iii, conductor 2l, right normalcontacts. of key 22, left closed contacts of said key to the ringconductor 32, extending to the selector switch S-I and connector switchC-2. The operator manipulates the dial I0 to transmit series `ofimpulses to the pulsing mechanism of the selector S-I and connectorswitch C-2. The selector and connector respond to these impulse seriesand step their brushes into engagement with the terminals of thesubscribers line 2. During each impulse series the @1T-normal contactsof the dial I9 close a short circuit around the coil 36 to improve thepulsing operation.

After the connector C-Z has been set on the terminals of the calledline, the operator moves the key 22 to its right-hand position. In thisposition a bridge is closed for holding the selector S-I and connector 02. This bridge may be traced from `conductor 29, left contacts of key22, coil 39, right closed contacts of key 22, left contacts of the keyto conductor 32. The key 22 also closes an operating circuit for relay33, traceable from battery through the contacts of key Il, winding ofsaid relay, conductor 311 to ground at the right contacts of key 22.Also the guard lamp i9 is lighted in an obvious circuit extending overconductor 34 to ground at the contacts of key 22. Relay 33 closes acircuit for sending a Seizure signal over the called line to operate thegas-lled tube 5 at the substation thereof.

This circuit may be traced from the positive pole of l20-volt battery35, resistance lamp 59, normal contacts of relay 35, winding of relay 31through the upper left winding of transformer 38, closed contacts ofrelay 33, conductor 39 thence through the tip brushes of the selectorS-I and connector (1 -2, conductor 40, through the upper primary windingof transformer 4I, printer magnet 4, resistance 42, condenser 43,resistance Ml, winding of relay 55, closed contacts of key i5 to ground.Current flowing in.

this circuit charges the condenser 43 until it reaches the ionizingvoltage of the control gap of the tube 5. When the ionizing voltage isreached, the tube res, and the anode circuit is established from thesource at the central office over the circuit traced through the printermagnet l to the anode lil and cathode 4.8 of the tube, thence throughthe winding of relay 45 to ground at the key 46. circuit to operate therelay l5 at the substation but not the relay 3l at the central ofce.Relay e5 at its right contact extends the circuit, above traced, throughthe magnet fi, through rectier 6I and relay 35 to ground, thus excludingtube 5. Relay t5 also closes a parallel circuit from source 35,resistance lamp 59, normal contact of relay 35, relay 3'I, lower leftwinding of coil 38, thence over the ring side of the line, conductor 53,left contact of relay 55, lower left winding of transformer 5I, magnett, right contact of relay 45, rectier 6I, winding of relay 45 to groundat key 46. Since these parallel circuits for magnet 4 short-circuit thetube 5, the latter becomes deionized. The increase of current due tothese parallel paths and the inclusion of low resistance rectier 6I inplace of the tube causes relay 3l to operate. Relay 3l at the centraloice extinguishes the guard lamp 49 and operates relay 35 in a circuitfrom battery through the contacts of key I'I, winding of relay 35, frontcontacts of Suicient current hows in this` relay 37 to .ground overconductor 34. Relay 36 locks through its own front contact directly tothe grounded conducto-r 34. The circuit for printer magnet 4 is `nowtransferred from l20 volt battery 35 to 80evolt battery 55 and may betraced from the latter through contacts of the operator-s telegraphsender magnet winding of printer 90, front contacts of relay 36, thenceas traced over the line in simplex through magnet 4., relay 45,rectifier 6|, relay 45,v and' ground at key 46. By excluding theimpedance of tube 5 suflicient current is derived from the reducedvoltage at central office to insure the continued operation of relay atthe lower voltage. The rectifier 6|, included in the circuit of relay45, prevents the relay from locking on `central oi'lice talking orsignaling battery.

Prior to the operation of relay 36 a. short circuit `exists across theconductors 33 and 5|) o-f the connection `extending to the calledsubscribers line. This short circuit may be traced from conductor 39through the nor- Inal contacts of relay 36 and the operated contacts ofrelay 33 to conductor 56. Between the time, therefore, that relay 33 isoperated and the operation of relay 36, no current `from the source 5|lio-ws over the called subscribers line. Instead of the short circuitfor disabling source 5| during this interval a contact on relay 36 couldbe used, if desired, to hold open the primary winding of transformer`38. As soon, however, as relay 36 yoperated as .above described, theshort circuit is opened and alternating current from the source 5| flowsin a loop circuit including the conductors of the called subscribiersline. This circuit may betraced from the upper left winding of thetransformer 38, closed contacts of relay 33, conductor 33, tip brushesof `selector S-I and connector C2, conductor 4D thence in parallelthrough the driving motor 3 of the printer and the primary windings oftrans former 4|, conductor 52, closed contacts of relay 45, conductor53, ring brushes of connector C-Z and selectors- L conductor 50, closedcontacts of relay 33 to the other terminal of the secondary winding oftransformer 38. The motor 3 is driven in this circuit to supply thenecessary .power for operating the printer. Also an alternating Voltageis induced inthe secondary winding of transformer 4 and the currentresulting therefrom is rectified by the rectifier 6 and applied to thewinding of relay Relay 'l operates and disconnects the telephone set 54from the line. Relay 'l also closes a short circuit around the relay 45and rectifier 6|, and relay 45 releases. Relay 'I now maintains theoperating circuit for Y the printer magnet 4 and the circuit forsupplying the alternating current to the transformer 4| and motor 3. Theprinter magnet operating circuit may be traced from the positive poleo-f battery 55 through the transmitting contacts of the operatorstelegraph transmitter Il, magnet winding of printer 90, closed contactsof relay 36, winding of relay 3l to the mid-point of the secondarywinding of transformer 38, thence in a simplex circuit through thecontacts of relay 33 over conductors 39 and 50 and conductors 40 and 53of the subscribers line, the conductor 46 extending through the upperprimary winding of transformer 4|, the conductor 53 extending throughclosed contacts of relay 1, conductor 52 and the lower primary windingof transformer 4|, the circuit 'continuing from the middle point of thevprimary winding through the printer magnet4, closedfcontacts of relay'l to .ground at the contacts of key 46. The alternating current circuitis the same as previously described, except that it now extends througha front contact of relay 'l instead of relay 45.

The circuits are now in condition for the sending of telegraph messagesto the called subscribers station. The operator proceeds to sendwhatever messages she may have for the absent subscriber by manipulatingher telegraph transmitter |I to send telegraph signals over the simplexcircuit through the printer magnet 4 at the called station. After themessages have been transmitted and recorded by the printer in thewell-known manner, the operator releases the connection she hasestablished to the subscribers line by restoring the key 22 to itsnormal or left-hand position. The restoral of the key removes groundpotential from conductor 34 and relays 33, 36 and 3l release. Relay 33opens the printing circuit and also opens the i circuit for supplyingalternating current to the motor 3 and transformer 4|. Thereupon relay lreleases, and the subscribers station is res stored to its normalcondition.

Should the `absent subscriber return to his telephone -and wish to makeuse of it while the opcrater is in the act of transmitting messages, hemay recover control of his telephone by operating the key 46. Theoperation of this key opens the printing circuit, allowing the relay 3lto release. The release of relay 3l lights the guard lamp 49 -steadilyto notify the operator that the subscriber wishes to use his telephoneand she should discontinue the further transmission of mess-ages. Shouldthe subscriber attempt to make use of his telephone without operatingthe key 46 at a time when messages are being transmitted he would hear atone through condenser produced by the alternating current flowing inhis line and would then realize that the operator was in the act ofsending messages to his substation.

The modified substation circuit shown in Fig. 3 differs essentially fromthe one disclosed in Fig. 1 in that the switching operations areperformed by an. auxiliary switch operating motor and by the printerymagnet, thus dispensing with the relays 1 land 45 and' with the rectier6 used in the arrangement of Fig. 1. The small auxiliary motor 62 isconnected in parallel with the printer motor 63 and is actuated by thesame source of alternating current at the central ofce. The printermagnet 10 and the motor 62 lboth act upon the switch operating spring 66to control the opening and closing of the associated electricalcontacts. When the magnet t6 is rst energized, its armature, actingthrough the insulating member 1|, urges the spring 66 upwardly out ofengagement with contact spring l2 and into engagement with spring i3.The spring 66, however, when thus operated by the full movement o-f theprinter magnet armature, does not close the contact springs 68 an-d 69.The motor 62, when energized, rotates a driven member 64 through a smallangle, causing the pin 65 to engage the spring 66. The spring 66 whenurged by the pin 65 engages insulating member 6l' and flexes `the spring63 into engagement with contact spring 69. When the spring 65 has beenmoved into engagement with spring 66, the resistance offered to furthermovement of these springs causes the motor 62 to stop in its partiallyrotated position where it remains, as long -as power is supplied to theline, to hold the contact springs in their i closed condition.

The operation of the modified circuit arrange'` ment will now bedescribed. When the 1Z0-volt battery 35 is connected to the tip and ringconductors of the line as hereinbefore described, current flows fromthis source over the tip conductor 'M through the upper winding '15.ofthe induction coil, winding of printer magnet l, resistances It and Tl,condenser 78 to ground. The condenser charges; whereupon the control gapof the tube i9 is ionized. An operating circuit for the magnet l' is nowclosed from conductor 'M through winding l5, magnet 'it through theanode and cathode gap of the tube 'i9 to ground. The printer magnet "niloperates in this circuit and moves the spring 66 out of engagement withspring 'l2 and into engagement with spring '03. The other path of thesimplex circuit for the magnet 'It may now be trace-d over the ringconductor St through springs 66 and '13, lower winding 8l of theinduction coil, magnet l0, thence through the tube to ground.

The opening of contact springs 66 and l2 disconnects the subscriberstelephone $2 from the line, and the closing of springs 66 and 'i3completes a circuit for supplying alternating current to the motors t3and t2. This circuit may be traced from the alternating current sourceat the central office over conductor 'l through the motors 63 and 62 inparallel, springs S and SB and thence over the other line conductor Si).The motor B3 rotates preparatory to the operation of the printer whensignals are subsequently received. The auxiliary motor G2 rotates thepin 65 into engagement with the partially operated spring 66, and thespring 66 is now fully operated to close the springs i3 and S9. When thespring 66 is in its fully flexed position the load on the armature ofthe printer magnet l is removed, leaving the magnet free and unhamperedto perform the printing selections when telegraph signals are received.When springs t8 and 69 are closed, the simplex operating circuit of theprinter magnet lil is diverted around the tube 19, and the tubethereupon deenergizes. One side of the revised simplex circuit for theprinter motor may now be traced from conductor l, winding 75, magnet 76,contacts 69 and 6B to ground; and the other side of the circuit may betraced from conductor 8%), contacts 56 and '13, Winding 8l, magnetsprings S9 and 68 to ground.

With this arrangement the substation circuit is prepared by theoperation of the printer magnet in response to the initial seizuresignal. This initial preparation closes the circuits for supplyingalternating current to the printer motor and to the auxiliary motor, thelatter of which performs a second switching operation to disconnect thetube and to place the printer magnet circuit in condition for thereceipt of the telegraph signals from the central office. The auxiliarymotor holds the substation circuits in condition for printing as long asalternating current is supplied over the line. After the messages havebeen transmitted the substation circuit is restored to its normalcondition by opening the alternating current circuit and permitting theauxiliary motor to return to its normal position under the influence ofthe switch operating spring 66.

if desired, the switching functions performed by the auxiliary motor maybe effected by a governor device actuated by the main motor of theprinter. Such a device is shown in Fig. 4. When the printer motor SGstarts, it operates lever 8l through the governor or centrifugal device88. Lever 81 operates the switch spring 89 and holds it in operatedcondition as long as motor 86 continues to run. Spring 89 performs thesame switching functions that spring 66 performs in the arrangement ofFig. 3. This arrangement dispenses with the necessity of an auxiliarymotor.

What is claimed is:

1. In a telephone system, a central office, a subscribers lineterminating therein, said line having a substation thereon, a telephoneat the substation of said line normally in operative connection withsaid line, a message recording device at said substation, means at saidsubstation controlled over said line for rendering said telephoneineiective and for operatively connecting said recording device to saidline, a source of current at the central office for operating saidrecording device over said line, and a signaling circuit including saidline for controlling said recording device to record messages.

2. In a telephone system, a central oicc, a telephone line terminatingtherein, a telephone for said line normally connected thereto, arecording device for said line normally disconnected therefrom, meanscontrolled over said line from the central office for disconnecting saidtelephone from the line and for operatively connecting said recordingdevice to said line, a source of current at the central oihce foroperating said recording device over said line, a signaling circuitincluding said line for controlling said recording device to recordmessages, and means responsive to the current flowing over said linefrom said source for holding said signaling circuit in condition for thetransmission of said messages.

3. The combination in a telephone system of a central office, asubscribers line terminating therein, said line having a substationthereon, a printer at the substation of said line normally disconnectedtherefrom, a space-discharge tube at said substation responsive to aseizure signal transmitted over the line for operatively connecting saidprinter to said line, a source of current at the central omce fordriving said printer, and a signaling circuit including said line foroperating said printer from the central office to record messages.

4. The combination in a telephone system of a central oiiice, asubscribers line terminating therein, said line having a substationthereon, a printer at the substation of said line normally disconnectedtherefrom, a motor for driving said printer, a source of alternatingcurrent at the central oilice for operating said motor, a spacedischargetube at said substation responsive to a seizure signal transmitted oversaid line, means responsive to the operation of said discharge tube foroperatively connecting said printer to the line and for closing acircuit over said line to supply current from said source to said motor,and a signaling circuit including the conductors of said line forcontrolling said printer to record messages.

5. The combination in a telephone system of a central oince, aSubscribers line terminating therein, said line having a substationthereon, a printer at the substation of said line normally disconnectedtherefrom, a motor for driving said printer, a source of alternatingcurrent at the central ofice for operating said motor, a spacedischargetube at said substation responsive to a seizure signal transmitted oversaid line, means responsive to the operation of said discharge tube foroperatively connecting said printer to the line and for closing acircuit over said line to supply current from said source to said motor,a signaling circuit including the conductors of said line fortransmitting message signals to operate said printer, and means at thesubstation operated in response to the current flowing over the linefrom said source of alternating current for maintaining said signalingcircuit closed during the transw mission of messages.

6. In a telephone system, a central office, a subscribers lineterminating therein, said line having a substation thereon, a telephoneat the substation of said line normally connected thereto, a messageprinter at said substation normally disconnected from said line, anoperators position in the central office, means under the control of theoperator for establishing a connection from her position to saidsubscribers line, means at the operators position for transmitting aseizure signal over the subscribers line, means at the substationresponsive to said signal for disconnecting said telephone and foroperatively connecting said printer to the line, a source of current inthe central oilice for driving said printer, a circuit over said linefor supplying current from said source to said printer, a signaltransmitter at the operators position, and means at the substation ofsaid line responsive to the current flowing thereover from said sourcefor holding said printer in operative connection to said line to receivesignals `from said signal transmitter.

7. The combination in a telephone system of a central oilice, asubscribers line terminating therein, said line having a substationthereon, a

printer at the substation of said line normally disconnected therefrom,a character selecting magnet for said printer, a motor for driving saidprinter, a source of alternating current at the central ofiice foroperating said motor, means for sending a signal over said line toenergize said magnet, switching means responsive to` the energization ofsaid magnet for closing a motor operating circuit over which current islsupplied from said source to said motor, and means controlled by saidmotor in response to the flow of current in said motor operating circuitfor holding said circuit closed independently of said magnet.

8. The combination in a telephone system of a central oice, a telephoneline terminating therein, a printer associated with said line andnormally disconnected therefrom, a select magnet for said printer, amotor for driving said printer, a source of alternating current at thecentral ofce, a driving circuit including the conductors of saidtelephone line for supplying current from said source to said motor,means for sending a seizure signal over said line to operate saidmagnet, a switch operated in response to the energization of said magnetfor closing the driving circuit of said motor, an auxiliary motoropera-ted in response to the flow of current in said driving circuit forholding said switch in operated position to maintain said drivingcircuit closed independently of said magnet, and means for sendingmessage signals over said line to operate said magnet.

PAUL VN WELCH.

